Duty Cycle Correction Circuit Using Input and Delayed Signal Transitions

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Solution Overview

Problem

Conventional duty cycle correction (DCC) circuits in integrated circuit memory devices are limited by susceptibility to process, voltage, and temperature variations, and have a large intrinsic delay, restricting the duty ratios they can generate and affecting accuracy, especially when clock signals deviate significantly from a 50%:50% duty cycle.

Innovation Solution

A DCC circuit that maintains a duty cycle corrected signal by generating transitions responsive to input and delayed versions of the input signal, using a latch and transition generator circuit, along with a delay control unit and adjustable delay line, to accurately adjust the duty cycle based on phase differences, allowing for flexible generation of various duty ratios, including 50%:50%.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional DCC circuits are used, then duty cycle correction is provided, but the circuits suffer from large intrinsic delay and susceptibility to process, voltage, and temperature variations

Engineering Contradiction:

Improveaccuracy of duty cycle correctionVSAvoidintrinsic delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The DCC circuit is divided into multiple independent components: a phase detector that measures phase difference, a duty cycle generator that creates correction signals based on the measured phase difference, and a signal combiner that merges the correction signal with the input clock. This segmentation allows each component to be optimized independently, reducing overall intrinsic delay while maintaining correction accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces conventional analog DCC mechanisms with a digital-based approach using phase detection and digital signal processing. The phase detector uses digital logic to measure phase difference, and the duty cycle generator uses digital counters and logic circuits to generate correction signals, eliminating the large intrinsic delays associated with analog correction circuits.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If conventional DCC circuits are used, then duty cycle correction is provided, but the control hardware is complex

Engineering Contradiction:

Improveaccuracy of duty cycle correctionVSAvoidcontrol hardware complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The phase detector is designed to serve multiple functions: it detects phase difference between clocks, generates control signals for the duty cycle generator, and provides timing references for the overall circuit. This multi-functionality reduces the need for separate dedicated circuits, thereby simplifying the overall control hardware while maintaining correction accuracy.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The duty cycle generator automatically adjusts the correction signal based on the phase difference measurement without requiring external control logic. The circuit self-regulates by using the phase detector's output to directly control the correction signal generation, eliminating the need for complex external control hardware.

Inventive Principle:

Principle #25Self-service

3Adaptability or versatility

If conventional DCC circuits are used, then duty cycle correction is provided, but flexibility in generating various duty ratios is limited

Engineering Contradiction:

Improveflexibility in generating duty ratiosVSAvoidaccuracy when clock signals deviate from 50%:50% duty cycle

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The duty cycle generator is designed with dynamic control capability, allowing the duty ratio to be adjusted based on the measured phase difference. The circuit can generate any duty ratio from 0% to 100% by varying the control signal width, providing full flexibility while maintaining precision through the phase-based control mechanism.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the control parameter from fixed duty cycle to variable duty cycle based on phase difference measurement. By using the phase difference as the control parameter, the system can accurately generate any desired duty ratio, including cases where the input clock deviates significantly from 50%:50%, thereby improving both flexibility and measurement precision.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7839193B2Duty cycle correction circuits including a transition generator circuit for generating transitions in a duty cycle corrected signal responsive to an input signal and a delayed version of the input signal and methods of operating the same

Publication Date: 2010.11.23 POSTECH ACADEMY INDUSTRY FOUNDATION

AI summary

A duty cycle correction circuit is operated by maintaining a state of a duty cycle corrected signal, generating a first transition in the state of the duty cycle corrected signal responsive to an input signal, and generating a second transition in the state of the duty cycle corrected signal responsive to a delayed version of the input signal.